In metal machining processes such as cutting and grinding, a metalworking oil agent is used for improving machining efficiency, for preventing abrasion between a workpiece and a tool for machining the workpiece, for prolonging tool life, for removing metal chips, and for other purposes. Such metalworking oil agents include an oil-base agent predominantly containing an oil component such as mineral oil, animal and vegetable oil, or synthetic oil, and a water solubility-imparted agent prepared by incorporating a compound having surface activity into an oil component. From the viewpoints of effective utilization of resources and fire prevention, a water-solubility-imparted agent (referred to as “water-soluble metalworking oil agent”) has come to be used more and more in recent years.
For the water-soluble metalworking oil agent (cutting or grinding oil agent), the following performances are demanded.
(a) Machining performance: Under circumstance where an improvement of productivity is demanded, it is considered to be needed to realize more efficient machining. In addition, an oil agent suited for every metal material species is needed.
(b) Rotting resistance: When water and an organic material coexist, rotting deterioration advances, whereby an oil agent performance is lowered.
(c) Emulsion dispersion stability: For the purpose of imparting lubricity, it is need to stably emulsify and disperse a water-insoluble lubrication component in water; however, since water and oil coexist, the metalworking oil agent is in an unstable state. In addition, metals which are eluted from a material to be worked, or the like further make the emulsified and dispersed state unstable.
(d) Stability of undiluted liquid: The form in which the metalworking agent is kept in the production site is an undiluted liquid; however, in many cases, in order to decrease a risk of fire during the storage, water is incorporated. Since water and oil coexist, the metalworking oil agent is in an unstable state. In addition, an undiluted liquid of metalworking oil agent (cutting or grinding oil agent) is often stored outdoors in a state where it is put in a container or the like, and it is exposed to high temperatures in summer and to low temperatures in winter, respectively. Even under such circumstances, it must be stable.
Accordingly, for the purpose of improving machining performance of cutting or grinding or plastic machining, it is proposed to incorporate a linear olefin (α-olefin) having 6 to 40 carbon atoms (see Patent Documents 1 and 2). In addition, for the purpose of providing water-soluble cutting oil which is improved in cutting properties or grinding properties, is low in an offensive smell, is hardly rotted, and is good in defoaming properties, it is proposed to incorporate a salt of ricinoleic acid polycondensate (see Patent Document 3). Furthermore, for the purpose of improving antibacterial properties of a water-soluble cutting oil agent, it is proposed to incorporate an amine having a cyclohexyl group (see Patent Document 4).